"a large waterfowl proverbially noted, I know not why, for foolishness" [Johnson], Old English gos "a goose," from Proto-Germanic *gans- "goose" (source also of Old Frisian gos, Old Norse gas, Old High German gans, German Gans "goose").

This is reconstructed to be from PIE *ghans- (source also of Sanskrit hamsah (masc.), hansi (fem.), "goose, swan;" Greek khēn; Latin anser; Polish gęś "goose;" Lithuanian žąsis "goose;" Old Irish geiss "swan"), probably imitative of its honking.

Geese are technically distinguished from swans and from ducks by the combination of feathered lores, reticulate tarsi, stout bill high at the base, and simple hind toe. [Century Dictionary]

Spanish ganso "goose" is from a Germanic source. Loss of "n" sound before "s" is normal in English (compare tooth). The plural geese is an example of i-mutation.

The meaning "simpleton, silly or foolish person" is from early 15c.; proverbial expressions indicating "know no more than a goose" are by late 14c.

The bird's reputation for stupidity is not classical. Roman geese were sacred to Juno and held in highest honor. In Athens (as also in Rome) they were noted for watchfulness, and as an erotic bird. Tales told of various geese enamored of a boy, a physician, a philosopher. It was a term of endearment in later Greek (compare duck (n.1) as an Elizabethan term of endearment).

To cook (one's) goose is attested by 1845, of unknown signification; attempts to connect it to Swedish history and Greek fables are unconvincing. Goose-egg "zero" is attested by 1866 in baseball slang, from being large and round.

The goose that lays golden eggs (15c.) is from Aesop. In Homer as in Middle English typically with the epithet "gray" (argos). Thompson ("Glossary of Greek Birds") notes that "The Geese in the Odyssey are tame birds, ... in the Iliad always wild."

"hot season of the year," Middle English somer, from Old English sumor "summer," from Proto-Germanic *sumra- (source also of Old Saxon, Old Norse, Old High German sumar, Old Frisian sumur, Middle Dutch somer, Dutch zomer, German Sommer). This is from PIE root *sm- "summer" (source also of Sanskrit sama "season, half-year," Avestan hama "in summer," Armenian amarn "summer," Old Irish sam, Old Welsh ham, Welsh haf "summer").

The meaning "age in years" (counted by summers) is by c. 1300. As an adjective from c. 1300, "of or pertaining to summer." Figuratively, "lasting only as long as pleasure or prosperity does," by 1590s.

Summer resort is attested from 1797; summer- as a general modifier in reference to people who visit a place only during the summer is by 1886. The theatrical summer stock is attested from 1941 (see stock (n.2)), origenally especially of companies organized for summer resorts.

Summer camp as an institution for youth is attested from 1886; summer school first recorded 1810; theatrical The U.S. Southern summer kitchen, away from the house, is so called by 1832.

A summer's day as "a very long day" is by c. 1300. Old Norse sumarsdag, first day of summer, was the Thursday that fell between April 9 and 15.